Physiological, biochemical and root exudate response of maize seedlings to hydrogen sulfide applications

The effects of hydrogen sulfide (H2S), re-leased from the donor sodium hydrosulfide (NaHS), on maize seedlings grown hydroponically for 6 days were investigated. Plant biomass, malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide (O2 center dot-) content, and root exudates (organic acids) were measured. Results showed that 100 and 200 pM NaHS is the most appropriate and suitable concen-tration for the growth and development of maize seedlings, without affecting the MDA and H2O2con-tents but altering the O2 center dot-. In addition, high concen-trations of 500 and 1000 pM NaHS adversely af-fected these parameters compared with the control (CK). The pH of the root exudates declined under NaHS treatments. The organic acids in the root ex-udates, including fumaric, acetic, formic, and malic acids exhibited higher contents at 100 pM NaHS treatment, the lactic and citric acids were higher at both 100 and 200 pM NaHS. In contrast, oxalic acid was reduced at all NaHS concentrations compared with the CK. Low contents of all the organic acids analyzed were found under 500 and 1000 pM NaHS treatment. In conclusion, all the above pa-rameters were affected by the application of NaHS, while higher NaHS concentration was toxic for maize seedlings.